Preparation And Hydrogen Storage Properties Of Co/Mn Doped LaFeO₃-type Perovskite Oxide

Perovskite-type oxide(ABO3) shows some electrochemical activities in alkaline solution.The characteristics of low cost, easy activation and high discharge capacity make it possible to be applied to high-energy Ni/MH batteries in the future, so it have great research significance as Ni/MH battery cathode materials. In this article,La Fe1-xCoxO3 and La Fe1-xMnx O3(x=0~0.9) series of perovskite oxide were prepared by sol-gel method, and the electrochemical hydrogen storage properties of them were studied under different temperature. The composite electrodes were prepared by surface coating drop method, that is the La Fe0.6Co0.4O3 and La Fe0.7Mn0.3O3 electrode surfaces were coated with different amount of TiO2, and the electrochemical activities of the composite electrodes were studied under both dark and light conditions. The activation property, maxdischarge capacity and discharge capacity decline rate of the electrode were analyzed. The conclusions are as followed:XRD analysis shows that LaFe1-xCoxO3 and La Fe1-xMnxO3(x=0~0.9) series oxide belonge to a single phase of La FeO3 perovskite oxide; FTIR analysis shows that with the increase of Co/Mn, the infrared absorption peaks of 558-700 cm-1move to the direction of bigger wave numbers; SEM figure can be seen that although the sample reunion phenomenon is obvious, but the particle size presents transition from nanoscale to micron grade.Doping experimental results show that with the increase of doping amount,the maxdischarge capacity and cycle stability of the electrode of La Fe1-xMxO3 increased at first and then decreased, and the activation number decreased. When x=0.4 or 0.3, be namely LaFe0.6Co0.4O3 or La Fe0.7Mn0.3O3, the maxdischarge capacity reached maximum,and the discharge capacity decline rate reached minimum, and the activation property is also better.With the increase of charge and discharge temperature, the maxdischarge capacity of the electrode increased, at 333 K, after 30 times recharge cycles, the maxdischarge capacity of LaFe0.6Co0.4O3 and LaFe0.7Mn0.3O3 electrode reached 162.98 mAh/g and161.66 mAh/g, maxdischarge capacity increased 48.29 mAh/g and 42.81 mAh/g, the capacity decline rate of the electrode is lower, and the stability is better than 298 K.In dark box, the electrodes of LaFe0.6Co0.4O3 and La Fe0.7Mn0.3O3 coated by TiO2 showed less maxdischarge capacity and the activation property than that of the electrodes free from TiO2, and thicker coating layer, the less properties; But the cycle stability of the electrode improved as the amount of coating increases.Under the condition of illumination, the maxdischarge capacity and the activation property of La Fe0.6Co0.4O3 and LaFe0.7Mn0.3O3 electrodes, no matter coated with TiO2 or not, is much better than that in dark box. And the electrodes with TiO2 showed batter electrochemical properties than that without TiO2. The best result occured when the La Fe0.6Co0.4O3 and LaFe0.7Mn0.3O3 electrodes coated with 20% of TiO2 were tested,the maxdischarge capacity increased 32.87 mAh/g and 43.73 mAh/g compared with that in dark box, meanwhile the cycle stability of the electrode improved with the increase of amount of TiO2.